Relationships between uterine and fetal traits in rabbits selected on uterine capacity

• Published in: Journal of animal science 2003-05, Vol.81 (5), p.1265-1273
• Main Authors: Argente, M.J, Santacreu, M.A, Climent, A, Blasco, A
• Format: Article
• Language: English
• Subjects: animal ovaries; Animal productions; Animals; Biological and medical sciences; blood; body weight; death; Embryonic and Fetal Development - physiology; Fallopian Tubes - anatomy & histology; Female; fetal development; Fetal Weight; fetus; Fetus - blood supply; Fetus - physiology; Fundamental and applied biological sciences. Psychology; linear models; Litter Size - genetics; Litter Size - physiology; Mother. Fetoplacental unit. Mammary gland. Milk; Organ Size; ova; Ovariectomy - veterinary; ovulation; Ovulation - physiology; placenta; Placenta - blood supply; Pregnancy; Pregnancy, Animal; Pregnancy. Parturition. Lactation; probability; rabbits; Rabbits - anatomy & histology; Rabbits - embryology; Rabbits - physiology; Regression Analysis; Selection, Genetic; Terrestrial animal productions; uterus; Uterus - anatomy & histology; Uterus - blood supply; Uterus - physiology; Vertebrates; Vertebrates: reproduction
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/2003.8151265x

The aim of this study was to investigate whether uterine capacity (UC) in rabbits was related to uterine horn length and weight and whether these uterine traits and vascular supply were related to fetal development and survival. Data from 48 unilaterally ovariectomized (ULO) does of the High and 52 ULO does of the Low UC lines of a divergent selection experiment on UC were used. Does were slaughtered on d 25 of fifth gestation. The High line showed higher ovarian weight (0.08 g, P < 0.05) linked to a higher ovulation rate (1 ovum, P < 0.05) and greater length of the empty uterine horn. There were no differences between lines in the remaining doe traits. The number of implanted embryos and live fetuses, fetal survival, and uterine weight and length were positively associated and explained most of the observed variation. Average weights of the live fetuses and their fetal and maternal placentae were not related to uterine weight and length. The linear regression coefficient of full uterine horn length on the number of live fetuses was 2.43 ± 0.21. The weight of the full uterine horn showed a small quadratic relationship (P < 0.05) with the number of live fetuses. Full uterine horn length, after adjusting for the number of embryos, was negatively associated (P < 0.001) with the number of dead fetuses. The linear regression coefficient of average fetal placental weight of the live fetuses on number of implanted embryos was higher (P < 0.10) in the Low line (−0.23 ± 0.04 vs. −0.12 ± 0.04). The linear regression coefficient of average weight of the live fetuses on the average weight of their fetal placentae was higher (P < 0.10) in the High line (2.56 ± 0.47 vs. 1.27 ± 0.57). The High line was more efficient, most likely because an increase in intrauterine crowding has a lesser effect on the development of fetal placentae and fetuses. The fetal position within the uterus did not affect the proportion of dead embryos. Fetuses with placentae receiving a single blood vessel had a higher probability of death (P < 0.001) and the lowest weight. There was no difference between lines for individual weight of the live fetuses, but the High line showed higher individual weights of fetal (P < 0.01) and maternal placentae (P < 0.10). Live fetuses in the mid-portion of the uterus were lighter in weight (P < 0.05) than in the oviductal and cervical regions (20.3 vs. 21.6 and 21.7g). Increasing uterine capacity increases uterine length and decreases weights of fetus and fetal